introduced setMassFraction() in the compositionalfluidstate.hh so that
in case of mass fraction formulation, they can be set directly, the
converting to mole fractions is now handled by the
compositionalfluidstate class

some test failed (kuevette with 5% difference), new references are
committed, however maybe some thresholds have to be adapted

reviewed by kissinger


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@15433 2fb0f335-1f38-0410-981e-8018bf24f1b0